NASA/ADS

Abstract

Partial collision strengths for electron induced transitions in the beryllium-like ion Fe xxiii are calculated using the Belfast R-matrix programs te[(Berrington et al. 1995).]{be95} Our target has 98 fine structure states 1s(2 nl n'l' SLJ) corresponding to n = 2 and n' = 2, 3, 4 . The present calculation is carried out for electron impact energies in the range 3.15 to 350 Ry. Below 115.185 Ry, corresponding to the highest excited state of our model ion, we use the Breit-Pauli version of the R-matrix code. For energies between 116 and 350 Ry we use the non-relativistic LS-coupling version of the R-matrix code together with JAJOM te[(Saraph 1978).]{sa78} When T exceeds about ten million degrees one needs to take account of contributions to the thermally averaged collision strength sl Upsilon coming from electrons with energies in excess of 350 Ry. We discuss a way of estimating these contributions. Values of sl Upsilon are computed and tabulated as functions of log T for transitions between the 2s(2 ) (1S_0) , 2s2p (3P_{0,1,2}^o) , 2s2p (1P_1^o) , 2p(2 ^3P_{0,1,2}) , 2p(2 ) (1D_2) and 2p(2 ) (1S_0) states. The temperature range 6.3 <= log T <= 8.1 is centred on log T = 7.1 which, according to te[Arnaud & Rothenflug (1985),]{ar85} is where Fe xxiii has maximum coronal abundance.